<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="https://cdn.bootcss.com/jquery/1.10.2/jquery.min.js"></script>
    <style>
        .left,.right{with:200px;padding:10px;float:left;}
        .left{background-color: red;}.right{background-color: blue;}
    </style>
</head>
<body>
<div class="wrap">
    <div class="left">
        left
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        left
    </div>
    <div class="right">
        right
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        <br/>
        right
    </div>
</div>
<script type="text/javascript">
  $(document).ready(function(){
      if($('.left').height()>$('.right').height()){
          $('.right').css('height',$('.left').height())
          console.log(111);
      }else{
          $('.left').css('height',$('.right').height())
          console.log(222);
      }
  })
</script>
</body>
</html>